Many polymeric systems are known to contain trace amounts of acidic moieties which over time or processing produce undesirable side effects, e.g., color instability, odor, physical degradation, irregular cure patterns or corrosion of processing equipment. In order to overcome these limitations in polymeric systems, a type of additive, generally referred to as an acid acceptor or acid scavenger, is incorporated therein to preferentially react with these acid moieties to prevent or delay these undesired side effects.
It is known that thermoplastic polymers, which embrace both homopolymers and copolymers blend/alloys and elastomers, containing halogens derived from polymerization catalysts and/or attributed to the after-halogenation of the polymers, such as olefin polymers or copolymers produced by using Ziegler-type catalysts comprising a halogen-containing compound as a catalyst component and/or a carrier component, or the after halogenated products of these polymers, frequently corrode processing or compounding machines during their molding operation, or discolor or degrade the resulting molded articles, because of the halogens contained therein.
Compositions of poly(arylene sulfide) also often suffer from mold corrosion difficulties. It would be desirable to produce a poly (arylene sulfide) molded composition which exhibited low mold corrosiveness, improved insulating properties and retention of strength in moist environments.
It also has been found that when post-consumer thermoplastic polyolefin articles are subject to the recompounding and recycling process, offensive odors from absorbed contaminants (e.g. milk, halogens) inpart an offensive odor. Further, many post-consumer polyolefins suffer from unacceptable cross-linking during reprocessing as a result of these contaminants. Acid acceptors may also be used in post-consumer thermoplastics such as polyethylene, polypropylene, polyethylene terephthalate (PET), PBT, polyphenyl sulfide, and polyvinyl chloride, which contain undesirable organic acids from impurities, acidic moieties released during extensive processing or halogen containing polymer contaminants. Accordingly, acid acceptors may be employed to counter or ameliorate these difficulties.
An acceptable acid acceptor should preferentially react with the undesired acid moiety but should not have detrimental effects on the physical or mechanical properties of the polymers in which it is placed. Typical acid acceptors used in polymeric systems include hydrotalcite, lead oxide, calcium sterate, etc. Cross-linking polymer systems which typically employ acid acceptors include halogenated polyolefins, such as polyvinyl chloride, chlorofluoropolymers, and polyarylene sulfide which for purposes of this patent is considered a polyolefin.
The present invention provides for synthetic acid acceptor pigments which are particularly suitable for use in thermoplastic polymers containing trace amounts of detrimental acidic moieties or in curable thermoplastic polymers which utilize acid acceptors.